Let's all hope and pray that time travel isn't possible. There are certain concepts and ideas that if manifested into reality have so much incredible potential for good, have an equally devastating potential for evil. I trust myself more than anyone else on the planet and even I wouldn't trust myself with time travel. Ability to look into the future to some degree with the ability to avoid the most irredeemable events would be the most I would hope for. Any event that resulted in the destruction and extinction of the human race would be a worthwhile endeavor to prevent, but anything short of that seems like a bad idea to meddle in. Sometimes we have to get to the bottom before we aspire to change, sometimes that is the only way we can change.